Nostalgia & History > Q on EMD 1st and 2nd generation dynamic brakes

On EMD 1st and 2nd generation locomotives, during normal operation did the dynamic brake grids get hot enough to visibly glow at night? These grids inside the DB blisters are visible from ground level.

A friend and avid WP fan has a photo in his collection of a WP F-unit stopped past the bottom of a steep grade. There is a visible glow from the grids, reflecting inside the DB air intake plenum, and visible through the grill behind the cab.

-Bob

Under normal circumstances, NO.
If the grid blower motor had failed in the last minute before they stopped, the grids would have gotten red hot real quick. I don't know if they would have lasted a minute without burning up.

On the early first generation units, the grids could be easily overloaded at higher speeds, because all there was to protect them was a grid overcurrent relay which should open the excitation circuit. Under about 15 MPH, an F unit couldn't make enough current to slow down, let alone overheat the grids, consequently I suspect what your friend saw...
G

I agree with George; my observation after making numerous routine inspections as described below was that the grids should NOT be visibly 'glowing' if the cooling fans were operating properly.

As a young fireman, it was expected that when the engineer initiated dynamic braking, particularly at the beginning of a long grade, a trip back through the units to verify that the DB grid cooling fans were operating, was in order. Apparently this custom came about as a result of failures of the fans to reliably function as designed, with predictable and spectacular results.
If I found a fan not operating the procedure on those early generation units was to 'Isolate' the offending unit which would prevent the unit from providing both dynamic braking effort as well as tractive effort. Later units would be equipped with DB circuit breakers which only affected braking but still allowed
development of tractive effort.

On one memorable night time trip as a SP fireman on a helper based at Colton, CA we shoved behind the caboose on a westward drag freight up the long Beaumont Hill grade
west of Indio. Owing to our hours of service getting short the dispatcher decided to have us uncouple from the caboose while east of the apex of the grade at Beaumont and run our, now, lite engines on the adjacent main track around the train we had just helped up the hill.

This afforded us the opportunity to pass the freight while both their train and our helper engines moved westward down the west slope of the grade toward Colton.
Around El Casco we slowly caught up with the road engines of the train and as we passed them we could observe one of the rear units DB grids glowing a bright orange similar to that seen in your bread toaster at home. We told the crew but I don't remember now if they sent someone back to handle it.

Charlie



Edited 1 time(s). Last edit at 02/19/18 19:11 by cewherry.

A friend on the SP told of seeing fast eastbounds passing Alpine, TX with "glowing" dynamic brakes, he thought it was routine.
This in about 1% grade territory, 50 MPH or so for all trains.